Aoyagi Ritsuka (青柳立夏)
The protagonist of the story. He is just twelve years old, and quite mature for his age. He was born on December 21, and his bloodtype is B. He retains no memories before two years ago, and the reason for his amnesia is unknown. His mother, Misaki, is very unstable and became even more dangerous after Ritsuka's brother Seimei was murdered. Despite these enormous emotional blows, Ritsuka's ability to love unconditionally holds strong. No matter what anyone in his small circle of friends does, he loves them just the same. Still, this takes an enormous toll on his already fragile state of mind.
Though the Seimei mystery is a dominant element of the overall plot, Ritsuka's relationship with Soubi is the heart of the story. Apart, they are damaged, alone, and mostly devoid of hope. Together, they can find much-needed solace and compassion that no one else can give on the same level. No one else can understand on such a personal level the havoc wreaked on their emotions through Seimei's abandonment and the loss of childhood innocence through the heartless actions of authoritorial figures in their lives. Still, Ritsuka's frustration with Soubi's complex, contradictory personality just furthers their tense relations, but it lessens as he understands more about Soubi's past, and begins to just accept him as he is: a very flawed human being. Unlike anyone else, even Kio, Ritsuka doesn't try to use him, insult him, change him, or abuse him -- he just tries to understand.